In a use of electronic memory modules (memory chips, memory devices), it is important for an energy consumption not to rise in particular when there is an increase in the integration density.
FIG. 2 schematically shows a conventional memory device, a memory cell being illustrated schematically in the form of a capacitor C. In order to write an item of information to the memory cell C or in order to read the information from the memory cell C, it is necessary firstly to activate the corresponding word line WL. As a result of such activation, the transistor T is turned on and the stored charge in the capacitor corresponding to the stored information passes onto the lower bit line BLt illustrated in FIG. 2. Consequently, the potential difference between two bit lines, i.e. the bit line BLt connected to the transistor and a second bit line BLc, is altered. Before the memory cell C is addressed, the two bit lines have approximately an identical potential, while a potential difference between the bit line BLt and the bit line BLc (for example with respect to ground) is brought about during an addressing of the transistor T, which is connected to the memory cell C, via the word line WL.
The potential difference thus engendered between the bit line BLt and the bit line BLc is amplified and evaluated in a sense amplifier SA and subsequently written back again to the memory cell in order to maintain the information (electrical charge) stored in the memory cell for a relatively long time. Such reading of the information from the memory cell and writing of the information read out back to the memory cell is also referred to as a refresh mode, which, by way of example, has to be carried out at intervals of 64 milliseconds (ms) in the case of conventional memory cells.
The reading out and rewriting (writing back) of information (electrical charge) from and to the memory cell of a memory cell array is controlled by a central control unit of the memory device. In this case, current is required, i.e. electrical energy is consumed, for each memory cell of a memory cell array both when the information is read out and when the information is written back to the memory cell. In an inexpedient manner, all of the memory cells C of a memory cell array in a conventional memory device are connected directly to the sense amplifier SA, which is always designed in such a way that the potential difference is amplified and evaluated in the sense amplifier and subsequently written back again to the memory cell C.
In many applications, however, the information stored in the memory cell C is only required a single time, such that writing the information back to the memory cell C is superfluous. By way of example, in applications such as, for instance, in computation operations, it is merely necessary to maintain an item of information in the memory cell until the information is read out from the memory cell. After a single read-out, the information read out is processed, but is no longer required in the memory cell. Therefore, it is not necessary for the information read out to be written back to the corresponding memory cell of the memory cell array. If the writing-back operation (rewriting operation) is nevertheless performed, then a high current consumption and thus a high energy consumption of the overall memory device result, in a disadvantageous manner.